Sanofi Allstar Reusable insulin Delivery Device (Pen)

I am a regular user of your injection pen for injecting insulin. my daily intake is 22units when I fill with a new tube adjust for prescribed units there is no spring action the piston just slips again I adjust for the prescribed units it starts working again after taking injection for ten to twelve days the piston does not work ultimately 30 to 35 units left as un used this is the case for 3 years with 3 new pens I doubt that you have not done any quality control test before marketing it.